Diaphragm for electroacoustic transducer

ABSTRACT

A circular and uniformly vibratable type diaphragm for electroacoustic transducer of flat-plane driving types is provided. The diaphragm comprises a circular nonmagnetic and insulative membrane and a series of conductors formed on the membrane and comprises radial outlet parts extending as mutually spaced at regular intervals substantially from central field to peripheral field of the membrane, arcuate outlet parts extending in the peripheral field and connecting most of peripheral side ends of the radial parts, and central parallel parts to be subjected to magnetic fluxes of associated magnetic circuits as concentratively arranged in the central field and connected in series with the other central side ends of the radial parts. Remaining two peripheral side ends of the radial parts not connected are adapted to be input or output ends of the series conductors. The shape of the central parts of the conductors is advantageously similar U-shapes.

United States Patent [191 Tabuchi [451 Nov. 25, 1975 DIAPHRAGM FORELECTROACOUSTIC TRANSDUCER [75] Inventor: Shunichi Tabuchi, Okutarna,Japan [73] Assignee: Foster Electric Co., Ltd., Tokyo,

Japan [22] Filed: Jan. 2, 1975 [2H Appl. No; 537,939

[52] U.S. Cl. ..l79/l15.5 PV [5 l] lnt. Cl. H04R 9/02 [58] Field ofSearch 179/1 I5i5 PV, 181 R [56] References Cited FOREIGN PATENTS ORAPPLICATIONS 6.6l3,7l3 4/l968 Netherlands I, 179/! 15.5 PV

Primary ExaminerKathleen H. Claffy Assistant Examiner-George G. StellarAttorney, Agent, or FirmWolfe, Hubbard, Leydig, Voit & Osann, Ltd.

F Nit ABSTRACT A circular and uniformly vibratable type diaphragm forelectroacoustic transducer of flat-plane driving types is provided. Thediaphragm comprises a circular nonmagnetic and insulative membrane and aseries of conductors formed on the membrane and comprises radial outletparts extending as mutually spaced at regular intervals substantiallyfrom central field to peripheral field of the membrane, arcuate outletparts extending in the peripheral field and connecting most ofperipheral side ends of the radial parts, and central parallel parts tobe subjected to magnetic fluxes of associated magnetic circuits asconcentrativcly arranged in the central field and connected in serieswith the other central side ends of the radial parts. Remaining twoperipheral side ends of the radial parts not connected are adapted to beinput or output ends of the series conductors. The shape of the centralparts of the conductors is advantageously similar U-shapesi 6 Claims, 3Drawing Figures U.S. Patent Nov. 25, 1975 3,922,502

in g/ DIAPHRAGM FOR ELECTROACOUSTIC TRANSDUCER This invention relates toelectroacoustic transducers and, more particularly, to a diaphragm to beused for an electroacoustic transducer comprising a diaphragm made of anonmagnetic and insulative material having a series of conductors and aplurality of permanent magnets arranged as respectively opposed to eachother with pole surfaces of the same polarity through a slight clearanceon both surfaces of said diaphragm.

Conventional flat plane driving type speakers of this kind are of such astructure as shown, for example, in FIG. 1, wherein l is a diaphragmmade of a membrane of a nonmagnetic and insulative material, 2, 2', 2"and 3, 3', 3" are a plurality pair of elongated permanent magnets, eachof the respective pairs 2 and 3, 2' and 3', 2" and 3" of which isarranged as opposed to each other with magnetic pole surfaces through aslight clearance on both sides of the diaphragm l and in parallelrelation to adjacent pairs so that, while the magnetic poles of therespective pairs adjacent one another in expanding direction of thediaphragm 1 will be alternately of different polarities, the poles ofeach pair opposing will be of the same polarity. 4, 4 are parallel stripconductors formed on the diaphragm l by such a means as a printing orthe like so as to be respectively positioned intermediate between theadjacent magnets 2 and 2', 2' and 2" or 3 and 3', 3' and 3" whichconductors are connected at the respective ends with one another so asto be at least one zigzag shaped continuous conductor (as shown in FIG.2). 5 and 6 are soft iron plates bonded respectively on outside surfacesof the respective groups of the magnets 2, 2', 2" and 3, 3', 3" on eachside of the diaphragm 1 and one of them, for example, the iron plate 5,is provided with perforations 7 for allowing sounds to passtherethrough, between the adjacent magnets 2 and 2', 2' and 2" and soon. Dotted lines shown in FIG. 1 in spaces between the opposing andadjacent magnetic pole surfaces represent magnetic flux distribution.

The operation of the electroacoustic transducer shown in FIG. I shall beexplained next.

In the drawing, the opposing surfaces of, for example, the pair ofmagnets 2' and 3 are of N-pole and those of adjacent pairs of themagnets 2 and 3, 2" and 3" are S-pole, so that the magnetic flux will becaused to flow from the respective opposing N-poles to the respectiveadjacent S-poles so as to be substantially in parallel with the plane ofthe diaphragm l. The parallel sections 4, 4' of the continuous conductorare disposed thus in such magnetic flux at right angles with respect tothe flowing direction of the flux.

In case an electric current is passed through the continuous conductorin the above arrangement, the diaphragm l on which the conductor isprovided is subjected to an electromagnetic force effective in adirection perpendicular to the plane of the diaphragm. While thedirection of the electric current flowing each of the parallel sections4, 4' of the conductor is opposite to one another, the direction of themagnetic flux traversing each of such sections 4, 4' is also opposite toone another. Consequently, the diaphragm l is subjected to a drivingforce effective in a fixed direction, so that the electroacoustictransducer will be uti lized as a speaker operated in response to thedirection 2 and magnitude of the current passed through the stripconductor.

It is obvious that in case the diaphragm I is caused to be vibrated by asound contrarily to the above, there is produced an electromotive forcein the conductor on the diaphragm l vibrated, so that theelectroacoustic transducer will be able to be utilized as a microphone.

Now, the shape of such diaphragm as disclosed of the arrangement in theelectroacoustic transducers referred to is generally rectangular asshown in FIG. 2 where the series of conductors generally of copper,aluminium or the like material formed by, for example, a print-wiringprocess on the diaphragm membrane is in a zigzag pattern 8 so as tocorrespond to parallel rows of the elongated permanent magnets, or isoften circular as shown in FIG. 3 where the conductors are arranged in avortex shape 10 having concentric circular sections. Such circulardiaphragm having vortexshaped conductor may be used in combination withthe elongated permanent magnets of parallel arrangement but, in thiscase, the same driving effect at least as in the case of FIGS. 1 and 2cannot be expected so that it will be required to arrange the permanentmagnets in a special pattern other than the simple parallel pattern.

In either cases, further, the rigidity and elasticity of the diaphragmhaving the metal conductor thereon must be well balanced in order thatthe sound transducing or reproducing frequency bands of the transducerreferred to will be made uniform and also expanded. With this regards,the circular diaphragm having vortex conductor may be preferable whileconfronting'the above discussed problem. In the case of the rectangulardiaphragm, the elasticity of the same is hard to be uniform depending onthe extending direction of the respective conductor sections as theconductors act as a rib, so that the entire diaphragm is hard to vibrateuni formly. In the case of the circular diaphragm of vortex conductor,further, at least an end of the conductor comes to the centre of thecircular diaphragm and it will be necessary to connect such a pull outlead wire as a copper foil to the centre of the diaphragm, which willcause bad influences to occur in the vibration of the diaphragm.

The present invention has been suggested to solve such problems asreferred to in the above. According to the present invention, theproblems have been successfully solved by providing on the circulardiaphragm a series conductor comprising radial outlet parts arranged atsubstantially regular intervals as extended from the centre side to theperipheral side of the diaphragm, peripheral arcuate parts respectivelyconnecting peripheral side ends of said radial outlet parts with oneanother, and central parallel parts respectively connected with centreside ends of said radial outlet parts.

A main object of the present invention is, therefore, to provide adiaphragm for electroacoustic transducers enabled to obtain uniformvibrations and a flat transducing or reproducing frequencycharacteristic.

Another object of the present invention is to provide a circulardiaphragm having a conductor including linear and parallel sectionswhich intersect magnetic fluxes of associated magnetic circuits, so asto enable it possible to render the diaphragm vibration uniform and tobe used in combination with magnetic circuits that required none ofspecially designed arrangement of the permanent magnets.

The present invention shall now be explained in detail in the followingwith reference to a preferred embodiment as shown in accompanyingdrawing, in which:

FlG. is a fragmentary sectioned view of a general electroacoustictransducer showing essential parts thereof;

H65 2 and 3 are plan views of conventional diaphragms;

FIG. 4 is a plan view of a diaphragm of the present invention; and

FIG. 5 is a sectioned view of the diaphragm shown in FIG. 4 taken alonga line V V in FIG. 4.

Referring now to FIGS. 4 and 5, 11 is a circular diaphragm made of suchhighly nonmagnetic and insulating material as, for example, polyimide,polyester, mica, phenol or the like, 12 is a group of substantiallyU-shaped conductors, in which A, is an innermost part of the U-shapedconductors, A, is a second part of the U-shaped conductors arrangedoutside the innermost part A, and so on so that many U-shaped conductorsare arranged outside in the same manner. An end of the conductor part A,is extended outward so as to form a starting terminal 14 of the wholeconductors and the other end of A, is connected with one end of the nextconductor part A through a radial outlet part 16, arcuate outlet part16" and radial outlet part 16", the conductor A is connected at theother end with an end of a next U-shaped conductor part A, throughanother radial and arcuate outlet parts so that the respective U- shapedparts will be all sequentially connected in series, and an end of theoutermost conductor part is connected through similar outlet parts to anend terminal for the whole conductors. In this arrangement, the arcuateoutlet parts are preferably located at the peripheral section of thediaphragm where the same is fitted to a supporting ring 13.

That is to say, the conductors are print'formed on the diaphragm so asto have the input or output ends positioned on the supporting ring andhave the effective conductor parts for the magnetic driving concentratedin the central section of the diaphragm so as to render distributiondensity of such effective conductor parts to be high and thus theinertia at the central section of the diaphragm to be larger.

Further, the distribution density of the conductors disposed in therange between the central section and the peripheral section of thediaphragm, that is, of the radial outlet parts is made low as arrangedat regular intervals, so that the increase of the inertia in this rangeof the diaphragm by the conductors will be prevented,

a proper elasticity will be given and the diaphragm will be able tovibrate uniformly. Further, the material thickness of the centralconductor parts is to be properly selected so that the inertia at thecentral section of the diaphragm can be properly selected or controlledand, also, any desired elasticity of the diaphragm can be obtained byproperly selecting the thickness of the diaphragm material, Thus, with aproper combination of conductor distribution density and quality andthickness and the quality and thickness of the diaphragm and conductormaterials properly selected, a uniform transducing or reproducingfrequency characteristic will be able to be obtained while expanding thetransducing or reproducing frequency band.

It will be understood that the diaphragm of the present invention can bewidely used for speakers, headphones, microphones and the likeelectroacoustic transducers.

What is claimed is:

l. A diaphragm for electroacoustic transducers comprising a circulardiaphragm membrane of a nonmagnetic and highly insulative material, anda series of conductors formed on said membrane and including radialoutlet parts arranged substantially at regular intervals as extendedfrom central section to peripheral section of the circular membrane,arcuate outlet parts respectively connecting said radial outlet partswith one another at their ends on the peripheral side, and centralparallel conductor parts disposed substantially in the central sectionof the circular membrane and connected in series with the other centralside ends of the radial outlet parts.

2. The diaphragm according to claim I wherein said central conductorparts comprises a plurality of conductor parts of respectively similarU-shapes, and respective ends on the peripheral side of two of saidradial outlet parts are adapted to form both terminals of said series ofconductors.

3. The diaphragm according to claim 1 wherein said arcuate outlet partsare substantially disposed on the peripheral section of the diaphragmmembrane.

4. The diaphragm according to claim 2 wherein said U-shaped centralconductor parts are concentratively arranged in the central section ofthe diaphragm membrane so that distribution density of the seriesconductors will be high at the central section,

5. The diaphragm according to claim 1 wherein said series of conductorsis made of copper.

6. The diaphragm according to claim 1 wherein said series of conductorsis made of aluminium.

I i it

1. A diaphragm for electroacoustic transDucers comprising a circulardiaphragm membrane of a nonmagnetic and highly insulative material, anda series of conductors formed on said membrane and including radialoutlet parts arranged substantially at regular intervals as extendedfrom central section to peripheral section of the circular membrane,arcuate outlet parts respectively connecting said radial outlet partswith one another at their ends on the peripheral side, and centralparallel conductor parts disposed substantially in the central sectionof the circular membrane and connected in series with the other centralside ends of the radial outlet parts.
 2. The diaphragm according toclaim 1 wherein said central conductor parts comprises a plurality ofconductor parts of respectively similar U-shapes, and respective ends onthe peripheral side of two of said radial outlet parts are adapted toform both terminals of said series of conductors.
 3. The diaphragmaccording to claim 1 wherein said arcuate outlet parts are substantiallydisposed on the peripheral section of the diaphragm membrane.
 4. Thediaphragm according to claim 2 wherein said U-shaped central conductorparts are concentratively arranged in the central section of thediaphragm membrane so that distribution density of the series conductorswill be high at the central section.
 5. The diaphragm according to claim1 wherein said series of conductors is made of copper.
 6. The diaphragmaccording to claim 1 wherein said series of conductors is made ofaluminium.